Process for producing a thermoplastic resin sheet having a color band

ABSTRACT

A process is disclosed for producing a thermoplastic resin sheet having a band of color by feeding a molten thermo-plastic resin by an extruder into a sheet-forming flat die having a manifold and extruding said molten resin from an extrusion opening of said flat die, while forcing a stream of a colored molten thermoplastic resin through at least one injection port opened into the manifold of the flat die into a main stream of the molten resin extruded from the extruder and fed to the manifold, associating the main stream of the molten thermoplastic resin and the stream of the colored molten thermoplastic resin within the manifold while the main stream is flowing in the extrusion and widthwise directions in said manifold, and extruding the associated streams from the extrusion opening of said flat die.

United States Patent [191 Kiyono et al.

[ PROCESS FOR PRODUCING A THERMOPLASTIC RESIN SHEET HAVING A COLOR BAND [75] lm entors: Hiroshi Kiyono, l-ligashiyama-ku,

Kyoto; Junichi Nakashima; Yasuyu-- ki Fujisaki, both of Koga-gun, Shiga-ken; Yukio Ishigaki, Otsu-shi, Shiga-ken; Gen Endo, Kusatsu-shi, Shiga-ken, all of Japan [73] Assignee: Sekisui Kagaku Kogyo Kabushiki Kaishaal, Osaka, Japan 22 Filed: July 17,1970

21 Appl.No.: 55,763

[52] US. Cl. ..264/l7l, 161/199, 264/75, 264/211, 264/245 [51] Int. Cl ..B29f 3/12, 1332b 17/06 [58] Field of Search ..264/17l, 75, 211, 245; 161/199 [56] References Cited UNITED STATES PATENTS 3,354,025 11/1967 Aykanian etal. ..264/ l7l 3,405,425 10/1968 Buckley et al 264/171 3,423,498 1/1969 Lefevre ....264/173 2,985,556 5/1961 Rowland ..264/l7l Primary Examiner-Robert F. White Assistant Examiner-Jeffery R. Thurlow Att0rneySherman and Shalloway [57] ABSTRACT A process is disclosed for producing a thermoplastic resin sheet having a band of color by feeding a molten thermo-plastic resin by an extruder into a sheet-forming flat die having a manifold and extruding said molten resin from an extrusion opening of said flat die,

while forcing a stream of a colored molten thermoplastic resin through at least one injection port opened into the manifold of the flat die into a main stream of the molten resin extruded from the extruder and fed to the manifold, associating the main stream of the molten thermoplastic resin and the stream of the colored molten thermoplastic resin within the manifold while the main stream is flowing in the extrusion and widthwise directions in said manifold, and extruding the associated streams from the extrusion opening of said flat die.

3 Claims, 8 Drawing Figures 3.715420 SHEET 10F 3 PATENTED FEB 6 I975 PROCESS FOR PRODUCING A THERMOPLASTIC RESIN SHEET HAVING A COLOR BAND This invention relates to a process for producing a thermoplastic resin sheet having a color band.

Heretofore, a laminated safety glass comprising two opposing glass sheets and an interlayer of a sheet of a thermoplastic resin such as plasticized polyvinyl bu- .tyral interposed therebetween has been used as 'windshields of automobiles, airplanes and the like or window panes of buildings. The interlayer is produced usually by heating, kneading and melting a thermoplastic resin by means of an extruder, introducing the molten resin into a mold for shaping it into a sheetlike form, and extruding it through an extrusion opening to shape it into a sheet. The interlayer so obtained is generally colorless and transparent, and permits transmission ofmost of the light. So when it is used as a windshield of a vehicle such as an automobile, the driver receives sunlight directly on his face with the effects of glare.

For restricting the transmission of light through the windshield and impart an anti-glare effect to it, it is the practice to color the interlayer with a dyestuff or pigment invarious colors such as bluish green either entirely or partially so as to form a color band. When coloring the interlayer partially, it is desirable to provide a color-gradient between a colored part and a noncolored parts, making the color progressively lighter in shade towards the non colored part and thus obtaining a gradually fading effect. I

The production of a sheet having a color gradient between a colored part and a non-colored part by means of an extruder is known by US. Pat, No.

3,405,425. According to the method disclosed in the U.

.3. Patent, a pigmented molten thermoplastic resin is forced vertically through a plurality of discharge tubes 'onto the main stream of a molten thermoplastic resin at a part immediately before the extrusion openingof the sheet-forming die-The amount of the colored thermoplastic resin to be forced through each of the discharge tubes is controlled so as to provide a color gradient in the widthwise direction of the sheet being extruded. In this method, the width of a color band resulting from the discharge of the colored thermoplastic resin through the, respective discharge tube is substantially equal to the diameter of the discharge tube in the widthwise direction ofthe sheet being extruded. The method, however, requires a complicated apparatus and a strict control of the amounts of the colored thermoplastic resin, leading to a troublesome operation. Furthermore, according to this method, it is difficult to maintain the amount of the resin forced through each of the discharge tubes constant for a long period of time since the colored resin is introduced simultaneously from a number of discharge tubes. Consequently, it is difficult to produce a sheet having a constant color gradient in its widthwise direction with good stability over along period of time.

Theobject of the present invention is to provide a process and an apparatus for thecontinuous and steady production of a thermoplastic resin sheet having a color band with a gradually fading color gradient between a colored part and a non colored part, especially a sheet of plasticized polyvinyl butyral used as interlayers of glass laminates.

The invention will be more specifically described with reference to the accompanying drawings in which:

FIG. 1 is a perspective view showing schematically one example of producing a sheet having a color band by forcing a colored molten thermoplastic resin into a sheet-forming flat die having a manifold system;

FIG. 2 is a transverse sectional view of a flat die of a different type from that shown in FIG. 1, which shows a stream of a colored molten thermoplastic resin forced through an injection port opened into a manifold;

FIG. 3 is a sectional view of the flat die shown in FIG. 2, taken along the line IIIIII of FIG. 2;

FIG. 4 is a transverse sectional view of a flat die of another type, which shows a stream ofa colored molten thermoplastic resin forced through an injection port opened into a manifold;

FIG. 5 is a sectional view of the flat die shown in FIG. 4, taken along the line VV' of FIG. 4;

FIG. 6 is a transverse sectional view of a flat (lie of still another type, which shows a stream of a colored molten thermoplastic resin forced through an injection port opened into a manifold;

FIG. 7 is a sectional view of the flat die shown in FIG. 6, taken along the line VIIVII' of FIG. 6; and

FIG. 8 shows the sections in the widthwise direction of three sheets A, B and C having a color band obtained by the process of the invention.

Referring to FIG. 1, a flat T die 1 is connected to an extrusion opening of an extruder not shown, and provided with a resin inlet pipe 2 for feeding a main stream 9 of a molten thermoplastic resin to the flat T die, a manifold 3, a passage 4 for conducting the main stream of molten resin, said passage being opened into the manifold 3, a die-land 5 subsequent to the manifold 3, a die extrusion opening 6, and an injection port 7 for a stream 10 of a colored molten thermoplastic resin, said injectionport being opened into the manifold 3 and connected to an injection pipe 8 for the colored molten resin connected to a device for feeding the stream 10 of the colored molten resin, such as an extruder or pump (not shown).

It has now been found that a sheet of a thermoplastic resin having, a good color gradient is obtained. by providing at least one injection port 7 for the stream of a colored resin in the manifold 3 and injecting a stream of a colored resin under pressure. towards a main stream of a resin flowing in the extrusion and widthwise directions in the manifold 3. The flowing action of the main stream of the resin within the manifold 3 leads to the gradually fading of color.

The main stream 9 of the resin extruded by an extruder in accordance with the present invention is conducted to the flat die 1, and filled in the manifold 3. On the other hand, a stream 10 of a colored resin is forced by a forcing device (not shown) through the injection pipe 8, and injected into the main stream 11 of the resin within the manifold from at least one injection port 7. The stream, of the resin is then rectified by means of the die-land 5, and extruded through the die extrusion opening 6 into a sheet 12 consisting of a thermoplastic resin 13 and a colored thermoplastic resin 14.

The flat T die 1 shown in FIGS. -2 and 3 includes a passage 4 for introduction of a molten resin, a manifold 3a of a vertical section, a circular injection port 7a, a die-land 5 subsequent to the manifold 3a, and a die extrusion opening 6. A colored resin 14 injected ito the manifold 3a of the flat T die appears symmetrically in the widthwise direction of the resulting sheet, and a sheet 12 having a cross section shown in FIG. 8-A is obtained. In the flat T die 1 shown in FIGS. 4 and 5, a circular injection port 7a is provided at a position slightly away from the center of the manifold in its widthwise direction. The section of the manifold 3b is not circular, and its portion near the die-land is gently inclined in a straight line against its horizontal surface and terminates in the die-land 5. The angle of inclination to the horizontal surface is to 60, preferably 30 to 45. The use of a flat die having a gentle angle of inclination results in a less disorder of a flow of molten resin in the extrusion direction at the inlet portion of the die-land, and it is possible to extrude a sheet of good quality steadily.

A sheet extruded by means of the flat T die shown in FIGS. 4 and 5 has a section shown in FIG. 8-B. Since the injection port 7a is provided at a position slightly away from the center of the namifold in its widthwise direction, the section of the sheet assumes a form such that the colored resin 14 forced from the injection port 7a is spread in one flowing direction of the main resin stream within the manifold 3b.

In FIGS. 6 and 7, the horizontal section of an injection port 7b opened into a manifold 3b has a shape of ellipse elongated in the direction of the major axis or a shape resembling a vertical section of a wing of an airplane. The injection port 7b is positioned at a certain angle to a dotted line 15 being parallel to the central axis and passing the center of the injection port 7b of the manifold. As is shown in FIG. 6, the angle is such that the end of the injection port 7b near the center of the manifold 3b is nearer to the die-land than the other end. In other words, the end of the injection port positioned upstream of the flow of resin within the manifold in the widthwise direction of the manifold is nearer to the die-land than the other end of the injection port. This angle is in the range of 0 to 90, preferably 0 to 45. By forcing a colored molten resin from an injection port of the shape and inclination angle described above, there can be obtained a sheet having a color band oflarger width with a more gradual color gradient as compared with the case where the colored resin is introduced from a circular injection port.

The section of the sheet extruded from the flat die shown in FIGS. 6 and 7 is illustrated in FIG. 8-C.

The shape of the injection port may be circular, triangular or square. To obtain a good color gradient and an adequate width ofa colored portion, it is preferred to use such shapes as circle, ellipse, crooked ellipse, ellipse with one side elongated in the direction of the major axis, forinstance, a shape resembling the vertical section of a wing of an airplane, crescent, or a symmetrical half ofa crescent.

In the present invention, any type of extruder capable of heat-melting and extruding a thermoplastic resin can be used, and the examples are a single screw type or a twin screw type. As the sheet-forming flat die, there can be conveniently used such flat dies as a center-fed die (T die) and an end-fed die (L die).

An extruder is used as means for forcing the colored resin continuously into the manifold, and when the colored resin is of low viscosity, pumps are employed conveniently for this purpose.

The thermoplastic resins used in the present invention mean synthetic resins capable of being melted by heat, and included are, for instance, polyethylene, polypropylene, polystyrene, polycarbonate, polyvinyl chloride, polyamides, polyvinyl butyral, polyacrylates, and polyesters. The thermoplastic resin which forms the main stream in the flat die may be the same as or different from the colored thermoplastic resin; preferably both are polyvinyl butyral. When different kinds of resins are used for both, it is preferred that both have good compatibility.

The thermoplastic resins used in the invention may contain suitable plasticizers such as triethylene glycol di-(2-ethyl butyrate), triethylene glycol dihexoate, glyceryl monoleate, dibutyl sebacate, and di-(B-butoxy ethyl) adipate dialkyl phthalates, or fillers.

Suitable coloring agents used in the invention are any types of dyestuffs and pigments which have superior resistance to heat during the sheet-forming operation and to weather. The examples of the coloring agents include dyestuffs of the azo, anthraquinone, and quinoline types, and pigments such as titanium dioxide, carbon black, ultramarine blue, medium chrome green, medium chrome yellow, cadmium red, molybdate orange, phthalocyanine derivatives, and indanthrene derivatives. The use of the azo type dyes, anthraquinone type dyes and quinoline type dyes is convenient in the present invention since it ensures the production of a sheet having a uniform color and change in density because of their good dispersibility or diffusibility in the thermoplastic resin. These dyes and pigments may be used either alone or in admixtures of two or more.

If the main stream 9 of a molten thermoplastic resin extruded from an extruder is colored in a certain color, a stream 10 ofa resin to be forced through the injection port 7 should be colored in a color different from that of the main stream 9 of thermoplastic resin.

The preferred amount of the colored resin is about 330% by weight based on the amount of a sheet extruded from the extrusion opening of the flat die. By forcing the colored resin of the above-specified amount into the manifold, a thermoplastic resin sheet having a color band can be produced in a steady condition. If the amount of the colored resin is outside the range specified above, a band of color appearing on the sheet being extruded tends to fluctuate in density, and it is somewhat difficult to extrude the sheet with the change in color maintained uniform for a long time in the widthwise direction of the sheet.

The viscosity of the resin stream is in the range of 5 X It) to l X 10 poises, preferably in the range of l X 10' to 6 X 10 poises. The pressure at which the colored resin is introduced ranges from 25 to 500 Kglcm preferably from 50 to 400 Kg/cm The invention will further be described by the following illustrative Examples which in no way limit the invention.

EXAMPLE 1 A mixture consisting of parts by weight of polyvinyl butyral and 40 parts by weight of polyethylene glycol di-(2-ethyl butyrate) was kneaded and melted by an extruder, and fed to a sheet-forming T die of the type illustrated in FIGS. 2 and 3 at an extrusion rate of 35 Kg/hr. The T die [had an inlet 4 for molten resin connected to the extrusion opening of the extruder, a manifold 3a having a diameter of 1.57 inches and a circular section shown in FIG. 3 in which the center line crosses the center line of the inlet 4 at right angles and the length is 32 inches in total extending each 16 inches on both sides of the intersecting point of both center lines, a die-land 5 subsequent to said manifold, and a die lip 6 with a clearance of 20 mils. An injection port 7a having a diameter of 78.8 mils is provided at a central position in the widthwise direction of the manifold. The injection port 7a is connected to an extrusion opening of an extruder smaller in size than the above extruder. A mixture consisting of 100 parts by weight of polyvinyl butyral, 40 parts by weight-of polyethylene glycol di-(ethyl butyrate) and 0.2 parts by weight of a dark green dyestuff (a mixture of an anthraquinonic dye and an azo dye and consisting specifically of 5 parts ofSumiplast Blue A, 2 parts of Sumiplast Red PB, and 3 parts of Sumiplast Yellow FC, all being the tradenames of the dyes produced by Sumitomo Chemical Co., Ltd., Japan) was kneaded and melted by this smaller extruder, and forced continuously into the manifold at a rate of Kg/hr through the injection port.

A sheet extruded from the die lip of the T die was cooled while being slightly stretched in the extrusion direction, and a polyvinyl butyral sheet having a band of color 30 inches in width and mils in thickness was obtained at a rate .of 40 Kg/hr. The color was most dense at the central part of the sheet in its widthwise direction and became progressively lighter away from the center. The color gradient or change in color density was substantially the same for both sides of the central part. The color gradient of the sheet obtained above was as shown in FIG. 8-A. The light transmission at a point of the sheet apart from one end of the sheet by a given distance in its widthwise direction was measured in-accordance with the method described below, and the results obtained are shown in Table l. I

The light transmission was measured by means of a spectrophotometer. When there was no absorption of light, the light transmission was defined as 100 percent, and when there was no transmission of light, the light transmission was defined as 0 percent. Thus, the calculation was made on this basis. The wavelengths of 400 to 700 mp. were divided into 8 sections, and one specimen was subjected to the transmission measurement with respect to every one of these 8 sections. The eight data thus obtained were averaged.

EXAMPLE2 The procedure of Example I was repeated except that the manifold used was one in which the section cut by a plane intersecting the central axis of the manifold perpendicularly had the shape as shown in FIG. 5, and an injection port opened into the manifold was provided at a position 2 inches away from the center of the manifold as illustrated in FIG. 4. A polyvinyl butyral sheet having a band of dark green color 30 inches in width and 15 mils in thickness was obtained at a rate of 40 Kg/hr. The section of the sheet in its widthwise direction was as shown in FIG. 8-B. The color gradient of the color in the widthwise direction of the sheet was shown by the light transmission measurements given in Table 2 in the same manner as set forth in Example I.

TABLE 2 Distance from one end of the sheet in its widthwise Light transmission direction (inches) EXAMPLE 3 The procedure of Example I was repeated except as noted hereinafter.

One injection port of an elliptic shape having a maximum width of 2 mm and a length of 16 mm, as shown in FIG. 6, was provided with its end near the center of the manifold being positioned at a point 2 inches away from the center of the manifold. The injection port was inclined against a dotted line being parallel to the central axis of the manifold and passing the center of the injection port 7b at an angle of 30 so that the end of the injection port near the center of the manifold was nearer to the die-land subsequent to the manifold. The

amount of the colored plasticized polyvinyl butyral to be forced from the injection port was adjusted to 6 Kg/hr.

A polyvinyl butyral sheet having a band of color 30 inches in width and 15 mils in thickness was obtained at an extrusion rate of 41 Kg/hr. The section of the sheet was as shown in FIG. SC. The color gradient of the polyvinyl butyral sheet in its widthwise direction was very gentle. The light transmission measurements are given in Table 3.

TABLE 3 What we claim is:

1. A process for producing a thermoplastic resin sheet having a band of color by feeding a molten thermoplastic resin by an extruder into a sheet-forming flat die having a manifold and extruding said molten resin from an extrusion opening of said flat die, which comprises forcing a stream of a colored molten thermoplastic resin under a pressure within the range of from 25 to 500 kg/cm through at least one injection port opened into said manifold of said flat die into a main stream of the molten resin extruded from said extruder and fed to said manifold, said stream of colored molten thermoplastic resin being forced into said stream of molten resin in an amount of about 3 to 30 percent by weight based upon the weight of the thermoplastic resin sheet extruded from said extrusion opening, said stream of colored molten thermoplastic resin being forced into said stream of molten resin when said stream of molten resin is flowing in the extrusion and widthwise directions in said manifold, associating the main stream of the molten thermoplastic resin and the stream of the colored molten thermoplastic within said manifold, the viscosity of the associated streams of the resin in said manifold being in the range of 5 X 10 to 1 X 10 poises; and extruding the associated streams from the extrusion opening of said flat die.

2. The process of claim 1 wherein said thermoplastic resin is selected from the group consisting of polyethylene, polypropylene, polystyrene, polycarbonates, polyvinyl chloride, polyamides, polyvinyl butyral, polyacrylates and polyesters.

3. The process of claim 1, wherein the coloring agent is selected from the group consisting of azo dyes, anthraquinonic dyes, and quinoline dyes. 

1. A process for producing a thermoplastic resin sheet having a band of color by feeding a molten thermoplastic resin by an extruder into a sheet-forming flat die having a manifold and extruding said molten resin from an extrusion opening of said flat die, which comprises forcing a stream of a colored molten thermoplastic resin under a pressure within the range of from 25 to 500 kg/cm2 through at least one injection port opened into said manifold of said flat die into a main stream of the molten resin extruded from said extruder and fed to said manifold, said stream of colored molten thermoplastic resin being forced into said stream of molten resin in an amount of about 3 to 30 percent by weight based upon the weight of the thermoplastic resin sheet extruded from said extrusion opening, said stream of colored molten thermoplastic resin being forced into said stream of molten resin when said stream of molten resin is flowing in the extrusion and widthwise directions in said manifold, associating the main stream of the molten thermoplastic resin and the stream of the colored molten thermoplastic within said manifold, the viscosity of the associated streams of the resin in said manifold being in the range of 5 X 103 to 1 X 105 poises; and extruding the associated streams from the extrusion opening of said flat die.
 2. The process of claim 1 wherein said thermoplastic resin is selected from the group consisting of polyethylene, polypropylene, polystyrene, polycarbonates, polyvinyl chloride, polyamides, polyvinyl butyral, polyacrylates and polyesters. 